等待方法完成，然后再继续运行

Question

我正在尝试运行一种名为uploadProfilePhoto（）的方法，但是即使uploadProfilePhoto（）尚未完成运行，该方法调用后的代码也会先运行。无论如何，我可以先让uploadProfilePhoto（）先完成它的过程，然后再继续吗？

我尝试使用AsynTask，但仍然无法正常工作。似乎是因为doInBackground（）用于一系列代码，而不是方法。

AsyncTask

protected class MyAsyncTask extends AsyncTask<Void, Void, Void>
{
    @Override
    protected Void doInBackground(Void... params) {
        uploadProfilePhoto();
        return null;
    }
    @Override
    protected void onPostExecute(Void result) {
        Toast.makeText(ProfileSetup.this, "Account created successfully.", Toast.LENGTH_SHORT).show();
        mAuth.signInWithEmailAndPassword(email, password);
        startActivity(new Intent(ProfileSetup.this, MainActivity.class));
    }
}

uploadProfilePhoto（）

private void uploadProfilePhoto() {

    if (mImageUri != null) {
        final StorageReference imageReference = storageReference.child(System.currentTimeMillis() + "." + getFileExtension(mImageUri));

        storageTask = imageReference.putFile(mImageUri);
        storageTask.continueWithTask(new Continuation() {
            @Override
            public Task<Uri> then(@NonNull Task task) throws Exception {
                if (!task.isSuccessful()) {
                    throw task.getException();
                }
                return imageReference.getDownloadUrl();
            }
        }).addOnCompleteListener(new OnCompleteListener<Uri>() {
            @Override
            public void onComplete(@NonNull Task<Uri> task) {
                if (task.isSuccessful()) {
                    Uri downloadUri = task.getResult();
                    myUrl = downloadUri.toString();

                    String myid = getIntent().getStringExtra("uid");

                    DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Users").child(myid);
                    reference.child("profilePicUrl").setValue(myUrl);
                    finish();
                } else {
                    Toast.makeText(ProfileSetup.this, "Failed", Toast.LENGTH_SHORT).show();
                }
            }
        }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                Toast.makeText(ProfileSetup.this, e.getMessage(), Toast.LENGTH_SHORT).show();
            }
        });
    } else {
        Toast.makeText(this, "No image selected", Toast.LENGTH_SHORT).show();
    }
}

Answer 1

我可以想到两种方式

 storageTask = imageReference.putFile(mImageUri);
    storageTask.addOnCompleteListener(new OnCompleteListener<Uri>() {
        @Override
        public void onComplete(@NonNull Task<Uri> task) {
            if (task.isSuccessful()) {
                myUrl = task.getResult().toString();
                String myid = getIntent().getStringExtra("uid");
                DatabaseReference reference = 
                FirebaseDatabase.getInstance().getReference("Users").child(myid);
                reference.child("profilePicUrl").setValue(myUrl);
                startActivity(new Intent(ProfileSetup.this, MainActivity.class));
                finish();
            } else {
                Toast.makeText(ProfileSetup.this, "Failed", 
                Toast.LENGTH_SHORT).show();
            }
        }

实际上不是很干净而且不错的第二种方法应该被认为是一种不好的做法，但是知道替代方法也没有什么害处

您说了imageReference.putFlie(mImageUri);后就可以立即启动MainActivity

imgeReference.putFile(mImageUri);
startActivity(new Intent(ProfileSetup.this, MainActivity.class));

现在在MainActivity中

while(ProfileSetup.getImageUrl() == null){ // define a method to return the url
       Systemclock.sleep(500);            // if it is small image you can hote it will be uplaoded in seconds      
}
Picasso.with(this).load(ProfileSetup.getImageUrl()).fit().into(imageView); // the while loop terminates when your image gets uploaded because getImageUrl() did not return null , now you know image is there you can download and set it to imageView by using Piccaso 

使用这种方法，您不需要completeListener，但是我不建议这样做，因为它更复杂并且不会处理imageUploading的任何失败